Technological advances of the past decade have allowed a more thorough analysis of immune-mediated mechanisms of renal injury in experimental models of glomerulonephritis. Although the histologic pattern of glomerulonephritis is a phenotypically complex lesion involving both glomerular and interstitial compartments, clinicopathologic analyses suggest that severity and chronicity of interstitial inflammation correlates well with ultimate progression of renal disease. While many disease models have focused on humorally-mediated mechanisms of glomerular injury, the pathogenic role of cell-mediated interstitial events has been largely unexplored. The primary objective of the studies outlined in this proposal is to examine cell-mediated mechanisms of interstitial injury in murine model of lupus nephritis, chronic graft-vs- host disease. Preliminary studies in this model have demonstrated that a subset of autoreactive T cell clones derived from nephrotic kidneys adoptively transfers interstitial injury to naive syngeneic recipients. To more precisely define the nephritogenic T cell response in susceptible animals, the studies in this proposal include a comprehensive phenotypic and functional characterization of T cell clones isolated from diseased kidneys at distinct time intervals in the progression of glomerulonephritis. These studies will include both in vitro and in vivo analyses. Lymphocyte function studies, such as proliferation assays, helper function studies, and cytotoxicity assays will evaluate MHC restriction and antigen specificity of isolated T cell clones. Cytokine analysis will examine whether these clones correspond to a TH1 or Th2 phenotype. The nephritogenic potential of isolated clones will also be assessed with comprehensive histologic and functional studies of adoptively transferred renal lesions. Characterization of T cell receptor (TCR) gene usage in disease-associated clones will determine frequency and/or preferential usage of TCR variable region families. Comparative analysis of nucleotide sequences of TCR antigen-binding regions derived from distinct nephritogenic clones will also be conducted. Examination of T cell and MHC interaction at a molecular level will better define immune interactions which might propagate inflammatory lesions within the kidney and facilitate the design of treatment modalities that downregulate injurious host immune responses. In aggregate, this analysis should comprehensively characterize a T cell phenotype that elicits interstitial injury in a model of glomerulonephritis and provide novel insights into the pathogenesis of interstitial injury in lupus nephritis.